A method of polymerizing alpha-omega diynes

Abstract

 A method of cyclization of α,ω-diynes with a transition metal catalyst such as niobium or tantalum salts such as halogen to yield products such as dimers, trimers and higher polymers which may have benzocyclobutene groups, or none of these, depending on the size of n in the α,ω-diynes of the formula HC≡C(CH₂)_nC≡C-H.

Description

[0001] This invention relates to a catalyst and aryl-­cyclobutene terminated alkane or a bis(arylcyclobutene) alkane. More particularly, this invention relates to a niobium catalyst that yields bis(arylcyclobutene) terminated alkanes or products of cyclotrimerization of the acetylene groups to form substituted benzene groups. Specifically, this invention relates to a one step method for polymerizing 1,5-hexadiyne and related α,ω-diynes of usually up to about 12 carbon atoms in relatively high yields, usually 70 percent and higher than 80 percent to essentially 90 plus percent yield. The α,ω-diynes useful in this invention may be represented by formula
HC≡C(CH₂)_nC≡C-H
where the tribond is represented as and n has preferably an even value such as 2, 4, 6, 8, 10, 12, etc.

[0002] The polyarylcyclobutenes, also preferably designated as "polybenzocyclobutenes", are desirable compositions due to their high heat stability and chemical resistance. Consequently, they have been suggested for coatings, fibers and films and other uses. In general, these polyarylcyclobutenes are relatively expensive and their cost limits their usage. Also, their manufacture requires a number of chemical operations.

[0003] The α,ω-diynes are available and we have discovered how to polymerize the α,ω-diynes of about 6 to 12 or more carbon atoms to produce dimers, trimers and higher polymers relatively simply by use of a very cheap catalyst and ones that are readily available with little preparation cost.

[0004] The catalysts useful in this invention are the salts of the transition metals of the Periodic Table such as niobium or tantalum. The halogen salts of these metals are well suited for this purpose. Specific examples of useful catalysts are niobium chloride, niobium bromide, tantalum chloride and tantalum bromide. The catalyst where the nobium and tantalum are in the pentavalent states are the desirable ones. For instance, niobium pentachloride and tantalum pentachloride generally give more desirable results and are preferred over niobium bromide or tantalum bromide. The iodides are more expensive and the fluorides are dangerous and less desirable than the bromides and chlorides.

[0005] The niobium and tantalum salts, such as the halides preferably of chloride and bromide may be used effectively with cocatalysts of tin. For example, the tin salts of the halogens may be used and the tin iodide salt of tetravalent tin are preferred. Also, the tetra organo tin compounds, such as the tetraaryl tins of phenyl, tolyl and related compounds may be used as cocatalysts. These cocatalysts may enhance polymer yield as shown by Tables II and III.

[0006] The ratio of monomers to catalyst can affect the polymer yield, usually about 1 to 50-100 gives the better results, although ratios as high as 1 to 500 have been used.

[0007] The catalyst may be used without a solvent. The hydrocarbons can be used as a solvent. The catalysts are not as soluble in aliphatic hydrocarbons as they are in aromatic and cycloaliphatic hydrocarbons.

[0008] The α,ω-diynes useful in this invention contain acetylene groups located in the α and ω positions on the hydrocarbon. Usually they contain from about 6 to about 14 carbon atoms with those having 6 to 12 carbon atoms being preferred. Representative examples are 1,5-hexadiyne, 1,6-heptadiyne, 1,7-octadiyne, 1,9-decadiyne and 1,11-dodecadiyne.

[0009] We have discovered that our catalyst can dimerize, trimerize and produce polymers from the α,ω-diynes in relatively high yields at temperatures of ambient to 80°C preferably in a solution of a suitable solvent. Suitable solvents are benzene, toluene, xylene and related liquid hydrocarbons, such as cyclohexane and halo carbons such as carbon tetrachloride or methylene dichloride.

[0010] The polymerization product can be recovered or freed from unreacted α,ω-diynes by treatment with an alcohol such as methanol and separating the phases. The solid precipitated phase is removed by filtration and the solvent in the filtrate is removed under vacuum. The residue from the solvent removal can be recrystallized from diethyl ether or hexanes to obtain a relatively pure product.

[0011] The nature of this invention and its advantages may be understood more readily by reference to the following representative and exemplary examples where all parts and percentages are by weight unless otherwise indicated.

Example 1

[0012] A reaction flask was charged with 25 ml of benzene and 5.6 x 10⁻⁴ moles of niobium chloride and 0.03 moles of 1,5-hexadiyne and allowed to react with stirring at room temperature. The solution turned dark brown; and, after 5 hours, the mixture was poured into methanol and 0.1 gram of black residue was obtained by filtration. The solvent in the filtrate was removed by vacuum distillation to leave a crude product. This product was recrystallized first in hexane and then in ether to give 1,2-bis(benzocyclobutenyl)ethane in 70.8 percent yield and a conversion of about 80 to 85 percent.

Example 2

[0013] This example uses a mixture of NbCl₅SnPh₄ as the catalyst to trimerize 1,5-hexadiyne (1.5 ml) in benzene (15 ml) with niobium chloride (75 mg) and tetraphenyltin (115 mg). The reaction was run for 5 hours at room temperature and terminated by addition of 1 ml of methanol. After 2 hours the mixture was filtered to remove the insoluble precipitate formed by the methanol treatment. The solvent in the filtrate was removed in a rotovac distillation apparatus. The residue from the distillation was dissolved in hexane (75 ml) and boiled with animal charcoal. Then it was filtered through a pad of celite. The celite was washed with hot hexane (20 ml) and the washing added to the filtrate. Hexane was removed under reduced pressure to obtain the purified 1,2-bis(benzocyclobutenyl)ethane in a yield of 85.5 percent.

[0014] When the same reaction was run in toluene (same conditions) the yield of 1,2-bis(benzocyclobutenyl)-­ethane was 90.0 percent. Thus, toluene is a preferred solvent.

[0015] Molecular weight determination of the polymers was done by GPC with polystyrene as the standard and using the Chromatix molecular weight program. DSC and TGA were performed using duPont 1090 instrument.

Example 3

[0016] Polymerization of 1,9-decadiyne using NbCl₅ as a catalyst in toluene was carried out in a 2-neck, 250 ml flask fitted with a rubber septum and a gas adapter. The catalyst NbCl₅, 0.075 g, (2.7 x 10⁻⁴ moles), was weighed into the flask inside a glove bag to give an inert atmosphere. The gas adapter was then replaced by a condenser. Freshly distilled benzene (25 ml) was injected into the flask. The flask was then warmed to 55°C. The monomer 1,9-decadiyne, 2.0 g (0.014 moles), was added in drops. The reaction was exothermic and the color changed instantly from deep red to black. The run was stirred for 5 hours, after which 3 ml of methanol was added to quench the reaction. The mixture was then poured into 200 ml of methanol and stirred for 2 hours. The precipitate was filtered and was vacuum dried for 24 hours. Total weight of the polymer was 1.90 g (95 percent conversion) of which 85 percent was soluble in toluene.

Example 4A

[0017] Polymerization of 1,7-octadiyne using NbCl₅ as catalyst and tin tetraphenyl as cocatalyst was carried out in a stirred solution of 1:1 mixture of NbCl₅ (0.150 g, 5.5 x 10⁻⁴ moles) and tin tetraphenyl (0.237 g, 5.5 x 10⁻⁴ moles) in toluene at 80°C to which was added the monomer, 1,7-octadiyne. The color changed from dark red to black. The mixture was stirred for 5 hours and poured into 200 ml of methanol. A viscous polymer fluid precipitated that stuck to the walls of the beaker. After decanting the liquid, the polymer was dissolved in toluene, re-precipitated with methanol and the precipitate was dried under vacuum. The yield of polymer was 3.04 g (63 percent). The methanol soluble fraction (33 percent) was identified as 1,4-bis(benzocyclohexenyl)butane.

Example 4B

[0018] Polymerization of 1,11-dodecadiyne using NbCl₅ as catalyst was carried out in the same manner as for 1,9-decadiyne. To a stirred solution of NbCl₅, 0.110 g. (4.0 x 10⁻⁴ mole) and tin tetraphenyl (0.170 g) in toluene 30 ml at 65°C was added 1,11-dodecadiyne 3.2 g (0.019 mole) in drops. The reaction mixture was stirred and the product compared to the fluid product obtained in polymerization of 1,9-decadiyne. After 12 hours, the reaction mixture was poured into methanol and stirred for 2 hours to precipitate the polymer. It was removed by filtering and the filtrate was dried under vacuum for 24 hours. The weight of the polymer obtained was 3.16 g (or 98 percent). 95 Percent of this polymer was soluble in toluene.

Example 5

[0019] A number of experimental runs were made to polymerize 1,5-hexadiyne with different catalysts in different solvents. The runs were made at temperatures indicated and the polymer was recovered in accordance with the procedure of the examples. The monomer to catalyst ratio was 50. The specific catalyst, solvent, temperature, percent conversion and percent trimer produced by each run is shown in the following Tables I-VI.

TABLE I

Cyclotrimerization of 1,5-Hexadiyne with Different Catalysts in Different Solvents
Catalyst	Solvent	Temperature °C	Percent Conversion	Percent Trimer Yield
NbCl₅	Benzene	55	85	70.8
NbCl₅	Toluene	75	82-85	70.8
NbCl₅/Cocat*	Benzene	30	100	85.8
NbCl₅/Cocat*	Toluene	35	100	90.0
TaCl₅	Benzene	55	70	58.0
	Toluene	75	62	53
NbBr₅/CoCat	Toluene	80	95	35
Monomer to Catalyst = 50:1
Cocatalyst - Sn(C₆H₅)₄, (1:1)

TABLE II

Cyclotrimerization of 1,7-Octadiyne (n-4) and 1,6-Heptadiyne (n-3)
Monomer	Catalyst	Solvent	Temperature °C	Percent Conversion	Percent Trimer	Percent Polymer
1,7-Octadiyne	NbCl₅	Benzene	55	88	33	50
		Toluene	80	90-85	38	53
	NbCl₅/Cocat*	Toluene	80	100	33	63
	TaCl₅	Toluene	80	60	20	33
1,6-Heptadiyne	NbCl₅	Toluene	80	40	15	25 Insol.
	TaCl₅	Toluene	80	35	15	20 Insol.
Monomer/catalyst - 50:1

*Cocatalyst - Sn(C₆H₅)₄; Catalyst:Cocatalyst - 1:1

Temperature = 35°C

TABLE III

Effect of Catalyst Concentration on the Cyclotrimerization of 1,5-Hexadiyne by NbCl₅
Monomer:Catalyst	Percent Yield of Trimer
	Without Cocatalyst	With Cocatalyst
50:1	70.8	93.3
100:1	65.3	90.1
200:1	57.6	81.0
500:1	33.0	68.3
Cocatalyst - (C₆H₅)₄Sn
Solvent - Toluene
Temperature = 35°C

TABLE IV

Effects of Various Cocatalysts on the Cyclotrimerization of 1,5-Hexadiyne by NbCl₅
Cocatalyst	Percent Conversion	Percent Trimer
(C₆H₅)₄Sn	100	90.1
(n-Bu)₄Sn	100	91.4
(CH₃)₃SnCl	100	91.1
(n-Bu)₃SnCl	96	88.4
SnI₄	92	82.5
EtA1C₂	88	65.0
Cocatalyst to Catalyst Ratio - 1:1
Solvent - Toluene

Example 6

[0020] This example provides a method for producing aryl cyclobutene derivatives that have great value in preparing specific arylcyclobutenes which may be used in a conventional way or to yield polymers with reactive groups. Particularly desirable as a derivative is the trialkylsilyl derivative as it can be readily converted to other derivatives having a specific group in a predetermined position.

[0021] Equal molar amounts of the α,ω-diyne, for instance 1,5-hexadiyne and trimethylsilylacetylene are charged to a reactor and the catalyst, such as those of Tables V and VI, is added and the reaction is allowed to occur and the reaction mixture worked up by methanol treatment following the treatment of the examples.

[0022] Table V shows that the tetraphenyl tin cocatalyst materially reduces the yield of the aryl­cyclobutene trimethylsilyl derivative relative to the yield where the catalyst does not contain the cocatalyst.

[0023] Table VII shows the preparation details of the polymerizations run on 1,7-octadiyne (1,7-OD), 1,9-decadiyne (1,9-DD), and 1,11-dodecadiyne (1,11-DDD). Some comments on the results of the polymerization are appropriate. In the case of 1,7-octadiyne, Table VII reports only that portion of the polymer that is soluble in toluene; the remainder of the products, to account for the high conversion, was 1,4-bis(benzocyclohexenyl)-­butane. In the case of TaCl₅ as the catalyst, high conversions to polymers were obtained, but the products were gels and mostly insoluble. For the NbCl₅ or NBCl₅/Sn(C₆H₅)₄ catalysts, high conversions were obtained and the polymers contained little gel.

TABLE VII

Polymerization of HC≡C(CH₂)nC≡CH
Monomer	Catalyst	Solvent	Temperature °C	Conversion Polymer*
				Percent	Percent
n=4	a	Bz	55	88	55
	a	Tol	80	90-95	53
	b	Tol	80	100	63
	c	Tol	80	60	33
n=6	a	Tol	65	100	80
	a	Bz	55	95	85
	b	Tol	65	100	95
	c	Tol	65	100	20
	c	Bz	55	100	5
n=8	a	Bz	55	95	80
	a	Tol	65	90	85
	b	Tol	65	100	95
	c	Bz	55	100	0
		Tol	65	100	5

*Percent of polymer soluble in toluene; a=NbCl₅; b=NbCl₅/SN(C₆H₅)4; c=TaCl₅; Monomer: MCl₅=50:1; where M is Nb or Ta; Bz=benzene; Tol=toluene

[0024] The product from the polymerization of 1,4-diethynylbenzene was totally insoluble in common organic solvents. This polymer was studied by DSC and 13_c solid state) measurements.

[0025] While in accordance with the patent statutes only the best mode and preferred embodiment of the invention has been illustrated and described in detail, it is to be understood that the invention is not limited thereto or thereby, but that the scope of the invention is defined by the appended claims.

Claims

1. A method of reacting an α,ω-diyne to form products containing at least one of the class of dimers, trimers and higher polymers comprising contacting said α,ω-diyne either as a sole reactant or together with an alkyne with a niobium catalyst or tantalum catalyst to effect formation of a benzo product characterized as highly soluble to insoluble in benzene at 25°C.

2. The method of Claim 1 where the niobium catalyst is selected from the class of niobium halide and niobium halide reacted with tin aryl or alkyl or cycloalkyl compounds and the temperature of reaction is about ambient to 80°C.

3. The method of Claim 1 wherein the reaction is terminated by addition of a terminating agent to form a precipitate, removing the precipitate and washing and reprecipitating said precipitate from a solvent to give a product free of α,ω-diyne.

4. The method of Claim 1 wherein the α,ω-diyne is 1,5-hexadiyne.

5. The method of Claim 4 wherein the product is 1,2-bis(benzocyclobutenyl)ethane.

6. The method of Claim 1 wherein the α,ω-diyne contains from 6 to 14 carbon atoms.

7. The method of Claim 1 wherein the polymer contains a terminal arylcyclobutene group connected to an alkyl radical having at least 2 carbon atoms.

8. A method of reacting an α,ω-diyne of the formula H-C≡C(CH₂)n C≡CH where n is an integer 2 and higher to form a product containing at least one of the species of the class consisting of dimer, trimer or higher polymer comprising contacting said α,ω-diyne with a catalyst comprising a tantalum catalyst or a niobium catalyst, or salts of said catalyst or cocatalyst of said salts with tin salts or organic tin compound at a temperature of about 10°C to boiling point of the α,ω-diyne.

9. The method of Claim 8 wherein tantalum and niobium are present as salts of the halogens chlorine and bromine and the cocatalyst is a halide of tin or a tetraaryl tin.

10. The method of Claim 8 wherein at least part of the α,ω-diyne reacts with trialkylsilylacetylene to yield a product having at least one trialkylsilyl group.

11. The method of Claim 8 wherein at least part of α,ω-diyne polymerizes with an acetylene having the formula H-C=CR and R is hydrogen, trialkyl Si, alkyl halide, and trialkylaryl radicals.

12. The method of Claim 11 wherein R is trimethyl Si radical.

13. The method of Claim 1 wherein the polymerization occurs in the presence of an aromatic solvent selected from the class consisting of benzene, toluene, and ethylbenzene.

14. The method of Claim 8 wherein the polymerization occurs in the presence of an aromatic solvent selected from the class consisting of benzene, toluene and ethylbenzene.

15. The method of Claim 8 wherein the product contains a high percentage of polymers other than trimers.

16. The method of Claim 15 wherein the polymer contains little gel and is essentially soluble in toluene at 25°C.